Photographic paper.



capab NI D STATES. PATENT .OFFIOE.

AUGUSTE LUMIERE AND LOUIS LUMIERE, OF LYONMONPLAISIR, FRANCE.

PHYQTQGRAPHIC PAPER;

Speeifi'cation of Letters Patent.

Patented May 14, 1907.

' Application filed May 15. 1906. Serial No. 317,028.

To all 1421mm it may concern:

Be it known that we, AUGUs'rE LUMIiaRE and LOUIS LUMIERE, citizens of France, residing at Lyon-Monplaisir, France, have invented new and useful Improvements in Photographic Papers, of which the following is a specification.

The invention has for its object the preparation of silver salt photographic papers containing an excess of soluble silver salt and e of development by simple immersion in water.

It is knownthat silver salt papers containing an excess of salt, such as papers prepared with citrate of silver, can be slightly impressioned and then treated with a developer, such ashydroquinone, gallic. acid, or other developing sub stance, in acid solution for example, .which, V by actingupon the excess of soluble silver salts of the paper,. produces-reduced silver which gradually fixes on the image the impression of which the action of light.

Hitherto it has not been possible to introduce directly the developing substance. into the emulsion 'used in the preparation of photographic papers in order to permit of the development of the image by simple immersion in water; the addition ofa developing substance to the emulsion promotes in fact, at the end of a very short time, the reduction of the solublesilver salt. In carrying the inhas been commenced by photographic soluble silver vention into effect this inconvenience is remedied by the addition of sulfurcus acid either to the emulsion or to the developing substance which is added to it."

The following is an example of how one can proc red in the latter case by employing gallic aciil.

Make a twentyper cent alcoholic solution of gallic acid and introduce into it tencubic centimeters of liquid sulfurous acid for every one hundred cubic centimeters of solution. Add in the dark fifty cubic centimeters of this solution to every one hundred cubic centimeters of citrate emulsion. The emulsion thus obtained can be readily prepared and spread without incurring any darkening.

The above mentioned quantities can be modified Within large proportions. and they have only been. cited by way of example. I

What we claim as our invention and desire to secure by Letters Patent, is z- I The herein described article, consisting of an emulsion containing an excess of soluble silver salt, a developer and sulfurous acid.-

In testimony whereof we have signed our names to this specification in the presence of two subscribing witnesses.

AUGUSTE LUMIERE. LOUIS LUMIERE.

Witnesses: I GASTON JEAUNIAUX, P MARIN VACHON. 

